Abstract:
Nuclear magnetic resonance is a technique with a wide range of applications in
biological and chemical sciences. Developments in the methods for recoupling and
decoupling in solid-state nuclear magnetic resonance are of fundamental importance
for its use in studying the biomolecules. In this thesis, work on developing such pulse
sequences is presented. For recoupling, symmetry-based pulse sequences (CN
n and
RN
n )are well known and frequently used. Exponentially modulating recoupling
technique is a sequence which make use of a small oscillating eld in addition to a
comparatively strong rf eld to recouple e ectively at low power irradiation. Inspired
by strong points of these two techniques, here we present a new method EXPORTCN.
This o ers an e ective recoupling at low power and at high spinning conditions.
Some selection rules, based on the pulse sequence parameters are derived similar to
symmetry based sequences, allowing us to select particular interactions to recouple.
In an alternative settings these sequences may also be used for decoupling and along
these lines we show that the decoupling performance of EXPORT which is a member
of this new family is comparable to the TPPM. To improve the decoupling e ciency
further a third modulating eld was added (TOFU) which leads to further reduction
in resonance line width. Theoretical analysis of EXPORT-CN sequence for rst and
second order terms is shown and some simulations are presented to discuss the
role of homonuclear recoupling in order to facilitate the heteronuclear decoupling.
Decoupling experiments are performed to explore the behavior of the EXPORTCN
and TOFU sequences for decoupling and to compare them with TPPM. These
experiments show that the oscillating eld techniques are capable of decoupling
heteronuclear interactions e ectively. So using these oscillating eld with carefully
chosen amplitudes can lead to a better decoupling by systematical suppression of
the higher order terms.
